1. Field
Methods and apparatuses consistent with that exemplary embodiments relate to transmitting urgent data, and more particularly, to a method and apparatus for transmitting urgent data by embedding the urgent data in normal data while transmitting the normal data.
2. Description of the Related Art
Recently, wired network solutions, such as high-definition multimedia interface (HDMI) and digital interactive interface for video and audio (DiiVA), are widely used to transmit in-compressed audio/video (AV) data. Most wired network solutions include control protocols for controlling consumer electronics (CE) devices. One of the control protocols is an HDMI-consumer electronics control (CEC) protocol in which a separate transmission line is assigned for CEC in HDMI. The HDMI has a pass-through function, and thus a device supporting a different standard is connected to an HDMI device as a dongle so as to replace an HDMI cable. Here, HDMI-CEC messages are mapped one to one and transmitted through another data network.
FIG. 1 is a diagram illustrating a structure of a block used in an HDMI-CEC protocol.
Referring to FIG. 1, the block includes 8 information bits, an end of message (EOM) bit, and an acknowledgement (ACK) bit. The ACK bit indicates whether a receiver normally received the block.
In the HDMI-CEC protocol, the information bits in such blocks are gathered to form one message. The maximum 16 blocks form one message, wherein a first block is referred to as a header block, and the blocks following the first block are referred to as data blocks.
A network that does not include a separate CEC line is referred to as a non-CEC network. Examples of the non-CEC network include Ethernet, WiFi, and Bluetooth. FIG. 2 is a diagram schematically illustrating structures of data transceivers 210 and 220 of a general non-CEC network. The non-CEC network includes a bidirectional data channel, and thus the data transceivers 210 and 220 may transmit and receive a data packet between each other.
Referring to FIG. 2, a transmitter 211 of the data transceiver 210 generates a normal data signal 22 by receiving and performing modulation or encoding on normal data 21, and a receiver 221 of the data transceiver 220 generates and outputs normal data 23 by receiving the normal data signal 22 and performing demodulation or decoding corresponding to the modulation or encoding. If there is no error, the normal data 21 and the normal data 23 are identical. When the data transceiver 220 transmits normal data 24 through a transmitter 222, the data transceiver 210 receives normal data 26 through a receiver 212. When the transmitter 211 transmits a signal, an output of the transmitter 222 is in a high-impedance (Hi-Z) state, and vice versa. A wired network is described hereinabove, but it is obvious to one of ordinary skill in the art that the non-CEC network may be a wireless network.
FIG. 3 is a diagram for illustrating a case when two CEC devices 310 and 320 are connected through a non-CEC network.
Referring to FIG. 3, a CEC message generated by the CEC device 310 is transmitted to the CEC device 320 by using a data transmission method provided by the non-CEC network. In FIG. 3, a transmitter (TX) dongle 210-1 converts the CEC message to a message defined in the non-CEC network, and a receiver (RX) dongle 220-1 converts the message defined in the non-CEC network to the CEC message.
First, the CEC device 310 transmits the CEC message to the TX dongle 210-1. Upon receiving the CEC message, the TX dongle 210-1 transmits an ACK message to the CEC device 310. The TX dongle 210-1 converts the received CEC message into a data packet, and transmits the data packet to the RX dongle 220-1 through the non-CEC network. The RX dongle 220-1 converts the received data packet to the CEC message, and transmits the CEC message to the CEC device 320.
Here, if the data packet is not transmitted to the RX dongle 220-1 due to an error, the CEC device 320 may not receive the CEC message. However, since the CEC device 310 received the ACK message from the TX dongle 210-1, the CEC device 310 may determine that the CEC message has been normally transmitted to the CEC device 320.
For example, assuming that a video stream is transmitted from a Blu-ray disk player (BDP) to a digital television (DTV). When a one-touch play function from among CEC functions is executed in the BDP by a user, the BDP transmits an “image view on” message to the DTV so that the DTV enters an image output state. Then, the BDP transmits an “active source” message to the DTV so that the DTV converts to a corresponding HDMI connector. At this time, while transmitting the “image view on” message, the BDP receives an ACK message from the TX dongle 210-1 but the “image view on” message is not transmitted to the DTV, and the BDP transmits the “active source” message to the DTV anyway since the BDP determines that the “image view on” message has been transmitted to the DTV. Accordingly, the DTV receives the “active source” message while in a standby state. In this case, since the DTV simply checks that an active source has changed, the DTV is still in the standby state, but the BDP reproduces an image. The user checks that the DTV is not properly operating, and may continuously push a button.
If the TX dongle 210-1 transmits an ACK message to the CEC device 310 after transmitting the CEC message to the RX dongle 220-1 through the non-CEC network and receiving an ACK message from the RX dongle 220-1, the CEC message may be prevented from not being transmitted due to an error in the non-CEC network.
However in this case, the TX dongle 210-1 must receive the ACK message from the RX dongle 220-1 and transmit the ACK message to the CEC device 310 within about 1.9 msec, according to a CEC bit timing. However, such condition cannot be satisfied because when the CEC message is received while transmitting a data packet through the non-CEC network, the transmitting of the CEC message may be delayed due to the transmitting of the data packet.
FIG. 4 is a diagram for describing a transmission delay when a CEC message is received while transmitting a data packet.
Referring to FIG. 4, when the CEC message is received at a point of time t1, the CEC message is transmitted through the non-CEC network after a point of time t2, and thus the CEC message is delayed by at least a time t2−t1.
For example, when Fast Ethernet 100BASE-TX is used as the non-CEC network, the maximum delay time until the TX dongle 210-1 receives an ACK message from the RX dongle 220-1 may be 2.152 msec, and when WiHD 1.0 is used as the non-CEC network, the maximum delay time until the TX dongle 210-1 receives an ACK message from the RX dongle 220-1 may be 73.7 msec.
A length of the data packet may be reduced or the CEC message may be transmitted after stopping the transmitting of the data packet, but in this case, an overhead of the non-CEC network is increased, and thus transmission efficiency is decreased.